This invention relates in general to a MEMS valve for controlling the flow of fluid. In particular, this invention relates to an improved structure for an electronically switchable MEMS valve configured to control fluid flow in low pressure, high fluid flow applications.
MEMS (Micro Electro Mechanical Systems) are a class of systems that are physically small, having features with sizes in the micrometer range; i.e., about 10 μm or smaller. These systems have both electrical and mechanical components. The term “micromachining” is commonly understood to mean the production of three-dimensional structures and moving parts of MEMS devices. MEMS originally used modified integrated circuit (computer chip) fabrication techniques (such as chemical etching) and materials (such as silicon semiconductor material) to micromachine these very small mechanical devices. Today, there are many more micromachining techniques and materials available. The term “micromachined device” as used in this application means a device having some features with sizes of about 10 μm or smaller, and thus by definition is at least partially formed by micromachining. A micromachined device may also include both micromachined components and standard sized (larger) components.
Various MEMS devices have been proposed for controlling fluid flow within a fluid circuit. For example, U.S. Pat. No. 5,475,353, the disclosure of which is incorporated herein by reference, describes a micromachined electromagnetic switch that uses three magnets, including one permanent magnet and two soft magnets. The permanent magnet is mounted to a first conductive member, and the first conductive member is separated by an air gap from a second conductive member. A planar actuator coil is embedded in a dielectric, insulating layer and separated from the second conductive member by the insulating member. Application of a current in a first direction moves the permanent magnet toward a first one of the soft magnets and to an open position. When the current is removed from the coil, the permanent magnet remains attracted to the first soft magnet and in the open position. Application of a current in a second direction moves the permanent magnet toward a second one of the soft magnets and to a closed position. When the current is removed from the coil in this position, the permanent magnet remains attracted to the second soft magnet and in the closed position. The planar actuator coil however, does not have sufficient magnetic field strength to create the permanent magnet travel required for a high fluid flow valve.
Thus, it would be desirable to provide an improved structure for an electronically switchable MEMS valve that allows for fluid flow control in low pressure, high fluid flow applications.